Frogs are members of the zoological class called Amphibia.
Amphibians are cold-blooded (or poikilothermic) vertebrate
animals. They differ from reptiles in that they lack scales and generally return to water to breed.
They are one of three
types of Amphibians. Anura, also called Salientia, (frogs and toads), caudate (salamanders and newts) and caecilians (worm-like
Herps and Herpetology
Amphibians together with reptiles make up a larger group called Herps. The study of reptiles and amphibians is called Herpetology.
Herp comes from the Greek word herpeton, which basically means "creepy crawly things that move about on their bellies."
herptile is an individual herp. A person who keeps and breeds herps is called a herpetoculturist and the hobby is called herpetoculture.
When Frogs mate, the male frog tends to clasp the female underneath in an embrace called amplexus. He literally climbs
on her back, reaches his arms around her "waist", either just in front of the hind legs, just behind the front legs, or even
around the head. Amplexus can last several days! Usually, it occurs in the water, though some species, like the bufos on the
right mate on land or even in trees!
(photo courtesy of Emile Vandecasteele)
While in some cases, complicated courting
behavior occurs before mating, many species of frogs are known for attempting to mate with anything that moves which isn't
small enough to eat!
While in the amplexus position, the male frog fertilizes the eggs as they get are laid. Frogs tend to lay eggs single eggs
in masses, whereas toads usually lay eggs in long chains.
Some frogs leave after this point, but others stick around to
watch over the little ones. Some have very unusual ways of caring for their young. You'll learn about some of those later
in this tour!.
Frogs and Toads tend to lay many many eggs because there are many hazards between fertalization and full grown frogness!
Those eggs that die tend to turn white or opaque. The lucky ones that actually manage to hatch still start out on a journey
of many perils.
Life starts right as the central yolk splits in two. It then divides into four, then eight, etc.- until
it looks a bit like a rasberry inside a jello cup. Soon, the embryo starts to look more and more like a tadpole, getting longer
and moving about in it's egg.
Usually, about 6-21 days (average!) after being fertilized, the egg will hatch. Most eggs
are found in calm or static waters, to prevent getting too rumbled about in infancy!
Some frogs, like the Coast foam-nest
treefrog, actually mate in treebranches overlooking static bonds and streams. Their egg masses form large cocoon-like foamy
masses. The foam sometimes cakes dry in the sun, protecting the inside moisture. When the rain comes along, after developement
of 7 to 9 days, the foam drips down, dropping tiny tadpoles into the river or pond below.
Shortly after hatching, the tadpole still feeds on the remaining yolk, which is actually in its gut! The tadpole at this
point consists of poorly developed gills, a mouth, and a tail. It's really fragile at this point. They usually will stick
themselves to floating weeds or grasses in the water using little sticky organs between its' mouth and belly area. Then, 7
to 10 days after the tadpole has hatched, it will begin to swim around and feed on algae.
After about 4 weeks, the gills
start getting grown over by skin, until they eventually disappear. The tadpoles get teeny tiny teeth which help them grate
food turning it into soupy oxygenated particles. They have long coiled guts that help them digest as much nutrients from their
meadger diets as possible.
By the fourth week, tadpoles can actually be fairly social creatures. Some even interact and
school like fish!
Tadpole with legs
After about 6 to 9 weeks, little tiny legs start to sprout. The head becomes more distinct and the body elongates. By now
the diet may grow to include larger items like dead insects and even plants.
The arms will begin to bulge where they will
eventually pop out, elbow first.
After about 9 weeks, the tadpole looks more like a teeny frog with a really long tail.
It is now well on it's way to being almost fullgrown
Young Frog, or Froglet
By 12 weeks, the tadpole has only a teeny tail stub and looks like a miniature version of the adult frog. Soon, it will
leave the water, only to return again to laymore eggs and start the process all over again!
By between 12 to 16 weeks, depending on water and food supply, the frog has completed the full growth cycle. Some frogs
that live in higher altitudes or in colder places might take a whole winter to go through the tadpole stage...others may have
unique development stages that vary from your "traditional" tadpole-in-the-water type life cycle: some of these are described
later in this tour.
Now these frogs will start the whole process again...finding mates and creating new froggies.
Some frogs have tongues that are long and sticky that can be used to catch bugs. These roll out like an upside-down party
horn and snap at the bug! (YUMMY!)
Frogs with long tongues go by the "see it, snap at it" technique of feeding. Toads, on the other hand, like my firebellied
toads, have tiny tongues and have to snap at their food using their mouth. They often will stalk their food, much like a cat...creeping
up to it and then just as dinner is about to take off, they will *SNAP* and eat their meal!
DID YOU KNOW: When a frog swallows a meal, his bulgy eyeballs will close and go down into his head! This is because the
eyeballs apply pressure and actually push a frog's meal down his throat! *GULP*
Actually, yes! But not like in this silly picture!
Most frogs do in fact have teeth of a sort.
They have a ridge
of very small cone teeth around the upper edge of the jaw. These are called Maxillary Teeth.
Frogs often also have what
are called Vomerine Teeth on the roof of their mouth.
They don't have anything that could be called teeth on their lower
jaw, so they usually swallow their food whole. The so-called "teeth" are mainly used to hold the prey and keep it in place
till they can get a good grip on it and squash their eyeballs down to swallow their meal.
Toads, however, do NOT have any
Frogs can hear using big round ears on the sides of their head called a tympanum. Tympanum means drum. The size and distance
between the ears depends on the wavelength and frequency of a male frogs call. On some frogs, the ear is very hard to see!
Ever wonder how frogs that can get so LOUD manage not to hurt their own ears? Some frogs make so much noise that they can
be heard for miles! How do they keep from blowing out their own eardrums?
Well, actually, frogs have special ears that
are connected to their lungs. When they hear noises, not only does the eardrum vibrate, but the lung does too! Scientists
think that this special pressure system is what keeps frogs from hurting themselves with their noisy calls!
Frogs are one of the best leapers on the planet! Did you know that frogs can launch themselves over 20 times their own
length using those big strong legs of theirs? That would be like if you could jump 100 feet!
The average flea can jump up to 150 times its own length.
A kangaroo can leap about 4 1/2 times it's length.
can't jump at all!
As far as I know, the longest frog jump on record measured 33 feet 5.5 inches. It was made by a frog named Santjie at a
frog derby held in South Africa.
Frogs have very special skin! They don't just wear it, they drink and breathe through it.
Frogs don't usually swallow
water like we do. Instead they absorb most of the moisture they need through their skin.
Not only that, but frogs also rely on getting extra oxygen (in addition to what they get from their lungs) from the
water by absorbing it through their skin. Because frogs get oxygen through their skin when it's moist, they need to take care
of their skin or they might suffocate. Sometimes you'll find frogs that are slimy. This is because the frog skin secretes
a mucus that helps keep it moist. Even with the slimy skin, these frogs need to stay near water. Toads on the other hand have
tougher skin that doesn't dry out as fast, so they can live farther from water than most frogs.
In addition to jumping
in water, frogs and toads can get moisture from dew, or they can burrow underground into moist soil.
Frogs shed their
skin regularly to keep it healthy. Some frogs shed their skin weekly, others as often as every day! This looks pretty yucky...they
start to twist and turn and act like they have the hiccups. They do this to stretch themselves out of their old skin! Finally,
the frog pulls the skin off over it's head, like a sweater, and then (this is gross) the frog EATS IT!!!! (EEEEEWWW!)
It turns out that very little is known at all about the natural lifespan of frogs. Partially, this is because it's pretty
hard to track a frog all its life! (I guess they havent figured out a good way to put little tiny collars around their necks!)
However,some records show that in captivity, many species of frogs and toads can live for surprisingly long times. They
seem generally average somewhere between 4 and 15 years!
Recently I ran across a page where people were posting data about how long their species of frogs had lived in captivity.
The longest lifespan entered was a European Common Toad (Bufo bufo ssp.) at 40 years!!!!!
Frogs have to watch out for all kinds of enemies in the wild. There are a wide variety of frog predators. Animals that
eat frogs for snacks include snakes, lizards, birds, and various small animals like hedgehogs. Even under water frogs cant
be safe from hungry sharp toothed fish, swimming mammals like water shrews, and even diving birds! As if that wasn't bad enough,
frogs even have to watch out for other hungry frogs!
Because there are so many bad guys to watch out for, frogs and toads have come up with a large variety of forms of protection.
The largest enemy that frogs have isn't something as easily adapted to: Pollution!
Frogs are becoming particularly important
as factors in measuring the health of the global environment and in tracking how much ultra-violet light gets into our atmosphere.
For some years now, it has been noted that worldwide frog populations have been in the decline. Many species are on the verge
of extrinction, while others are thriving well. Only recently has this frog population change been linked to not only a decrease
in upper atmospheric ozone layer, but also an increase in low-atmosphere ozone due to pollution.